Sandy sediment-based solar evaporator for large-scale and scalable freshwater production under various water environments

Interface solar steam generation (ISSG) technology has immense potential for addressing the global freshwater crisis. However, its large-scale application faces challenges such as limited sources and high costs of photothermal materials, complex fabrication processes, and poor stability and controllability. In this study, natural Yellow River sandy sediments (SS), which are abundant, easily accessible, and representative of natural sands, were used to synthesize tannic acid (TA)-Fe (III)-coated SS (TA-Fe@SS) as a photothermal material using a facile surface modification strategy. An efficient TA-Fe@SS-based ISSG system was developed by manipulating the microstructure of the SS, including particle size, TA-Fe modification density, and stacking form, and the impact of microstructural changes on the water transport rate, light absorption, and photothermal conversion efficiency was systematically investigated. The enhancement mechanism of water evaporation at the TA-Fe@SS aggregate interface was also elucidated. Under optimal conditions, the TA-Fe@SS-based water evaporator achieved a remarkable water evaporation rate of up to 2.84 kg·m−2·h−1 and a solar evaporation efficiency of 172 %. Furthermore, the TA-Fe@SS exhibited durability in various water environments, including acidic/alkaline water, dye-contaminated water, and real seawater. Potential large-scale outdoor application models were provided, confirming the applicability of TA-Fe@SS under various conditions.